After endorsing Kamala Harris on X Sunday, former Republican Sen. Jeff Flake of Arizona praised the vice president’s foreign policy understanding and her proposal for tougher border restrictions on ABC News’ “This Week.”

With 37 days until Election Day, Flake said he gave his consent now because he could not take part in political activities in his role as ambassador to Turkey, from which he resigned on September 1.

“I think Republicans, in particular, believe in the rule of law, and it’s difficult to support a candidate who, after losing an election, tries to use presidential power to overturn that election,” Flake said Martha, host of ABC’s “This Week.” Raddatz. “This is anything but respect for the rule of law.” Other conservative Republicans feel the same way, he said.

In his endorsement, Flake wrote that he believes Harris will unite the country and “respect the will of the voters.” He also discussed his support in an interview with the Arizona Republic.

The former congressman and senator joins other prominent Republicans who have endorsed Harris, including former Vice President Dick Cheney and his daughter, former Rep. Liz Cheney of Wyoming.

Flake is one of a few Republicans who served in President Joe Biden’s administration, along with Cindy McCain, the widow of former Sen. John McCain of Arizona. Since leaving the Senate in 2019, Flake has been an outspoken critic of former President Donald Trump, calling on Republicans to “move away from Trumpism.”

Flake also endorsed Biden in 2020 on the first day of the Republican National Convention, along with dozens of former GOP members of Congress.

He said Harris should “court all voters,” especially moderate and conservative Republicans.

When asked about his interactions with Harris during his time as ambassador, Flake said she is ready to serve as commander in chief.

“We must support and work with our allies,” Flake said. “And she understands that.”

He pointed to Harris’ speech at the Munich Security Conference and each candidate’s approach to foreign policy during the ABC presidential debate.

“It was really sickening to watch the debate the other day and hear that the former president wasn’t even able to cheer for Ukraine,” Flake said. “This is a big issue for me.”

Raddatz pressed Flake on whether his endorsement would resonate with Arizona voters affiliated with The Church of Jesus Christ of Latter-day Saints, of which he is a member. Sen. Mitt Romney, R-Utah., another senior Mormon Republican who opposes Trump, has not endorsed Harris.

Flake disagreed and replied: “I can only speak for myself and for my location.”

Following her visit to the U.S.-Mexico border on Friday, her first in three years, Raddatz asked Flake for his thoughts on one of the vice president’s biggest vulnerabilities. A recent ABC News/Ipsos poll found that voters thought Trump was better suited to handle the margin over Harris by 10 points.

Flake said he was glad Harris visited the border and proposed tougher asylum restrictions. He pointed to her work as a prosecutor and attorney general and said, “She knows what’s important.” Harris’ campaign is aiming to gain traction on an issue of great importance to voters.

While in Congress, Flake supported a bipartisan immigration proposal, but it did not pass. When Raddatz pressed him on the Biden-Harris administration’s handling of the southern border, Flake said there needs to be stricter asylum policies.

He applauded Harris for signing the immigration bill that failed in the Senate after Republican opposition led by Trump killed the bill.

“She knows how to work in a bipartisan way, and if we’re going to do permanent immigration reform, she has to be bipartisan,” Flake said.